Apparatus for ascertaining and evaluating the transverse profile of the moisture content of moved webs of paper and the like

ABSTRACT

Apparatus for measuring the transverse profile of the moisture content of moving web material, especially paper, according to which individually and at least approximately simultaneously the moisture content at different areas across a moving web material is ascertained, and the thus obtained moisture content of the individual areas across the web to be measured are individually stored and conveyed to indicating means for controlling the moisture content of the respective web material.

United States Patent [191 Lippke Inventor: Paul Lippke, Walter-Rathenau- Strasse 14, 545 Neuwied, Germany Filed: Aug. 20, 1970 Appl. No.: 65,377

[30] Foreign Application Priority Data Aug. 21, 1969 Germany ..P 19 42 529.7

US. Cl. .;..162/263, 73/73, 162/252, 162/262, 324/61 M Int. Cl. ..D2lf 7/00, GOln 5/02 Field of Search ..162/198, 252, 262, 263; 73/73; 324/61 M, 60 CD References Cited UNITED STATES PATENTS 2/1971 Grant ...l62/252 UX 2/1971 Keyesetal ..'.....l62/l98 UX 1 Jan. 30, 1973 3,358,378 12/1967 Downs ..73/73 X 2,611,974 9/1952 Stratveit et a1. ..73/73 X 2,922,475 1/1960 Alexander ..162/252 3,260,642 7/1966 Canter, .lr ..162/252 2,951,007 8/1960 Lippke ..162/198 3,040,807 6/1962 Chope... .....162/252 1,708,073 4/1929 Allen ..73/73 X 2,373,846 4/1945 Olken ..324/61 M 2,997,649 8/1961 Kotilainen ..324/61 M Primary Examiner-81 Leon Bashore Assistant Examiner-Alfred D'Andrea Attorney--Walter Becker [57] ABSTRACT Apparatus for measuring the transverse profile of the moisture content of moving web material, especially paper, according to which individually and at least approximately simultaneously the moisture content at different areas across a moving web material is ascertained, and the thus obtained moisture content of the individual areas across the web to be measured are individually stored and conveyed to indicating means for controlling the moisture content of the respective web material.

3 Claims, 3 Drawing Figures PATENTEDJAUO ma 3,713,966

SHEET 10? 3 I wlb I N x Q N l M Q s KI mmvron 2% ZWJE BY 9 a I PATENTEDJMI 30 I973 SHEET 2 BF 3 INVENTOR. Pzo/ [W /a APPARATUS FOR ASCERTAINING AND EVALUATING THE TRANSVERSE PROFILE OF THE MOISTURE CONTENT OF MOVED WEBS OF PAPER AND THE LIKE The present invention relates to a method of and apparatus for ascertaining and evaluating the transverse profile of the moisture content of moved webs of paper and the like.

For ascertaining the transverse profile of the moisture content of moved webs of paper and the like,

traversing moisture gauges or the like have become known which are moved over the moving web in a transverse direction back and forth at a speed of, for instance, 2.5 meters per minute. The values ascertained by such moisture gauges are conveyed, for instance, to a registering instrument the feed of which or, more specifically, the feed of its registering tape, is synchronized with the traversing movement of the moisture gauge.

When preparing webs of paper, modern paper machinery realizes speeds of the paper web up to 1,000 meters per minuteLThe width of such webs may amount to, for instance, meters. When assuming a speed of 2.5 meters per minute for a traversing moisture gauge, approximately 2 minutes will pass until the moisture gauge moves from one edge of the web to the other edge. During this time, 2,000 meters of the web have passed by the moisture gauge. The assumed measuring track of the moisture gauge is a diagonal in a rectangle which has a length of 2,000 meters and a width of 5 meters. Since the moisture content of the web material may considerably vary over such a length, it will be appreciated that with such a measuring operation a genuine measuring of the moisture content of the transverse profile is at best approximate. Moreover, with a paper machine there exists the possibility that due to inaccuracies on the drying areas periodically changes in the moisture content of the web material may occur which are frequently uniform over the entire length of the web. In view of this fact, it is impossible by means of a traversing moisture gauge to obtain a genuine distribution of the moisture content over the width of the web. Accordingly, in view of the values ascertained in this way, a satisfactory control of the moisture content will be impossible. Similarly, a fast and precisely working control on the basis of this measuring method is impossible.

It is, therefore, an object of the present invention to provide a method of and apparatus for ascertaining a genuine transverse profile of the moisture content of a moving web, especially paper web, to thereby permit a precise registering and evaluating of the transverse profile of the moisture content of the web being moved.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 diagrammatically illustrates a moisture gauge according to the invention in connection with a web being moved.

FIG. 2 shows by way of example a circuit while employing a moisture gauge according to the invention operating in conformity with the principleof a dielectric measuring.

FIG. 3 shows a section through a carrier or support for the moisture gauge according to which openings are provided to permit suction air to act upon the web being moved.

The method according to the present invention is characterized primarily in that a number of moisture gauges is employed which number preferably corresponds to the number of the breast box lips of the paper making machine, while said moisture gauges are arranged adjacent to each other in a direction transverse to the direction of movement of the web and are parallel to the plane of said web. The values measured by the moisture gauges are during a measuring operation simultaneously or with regard to the speed of the web approximately simultaneously fed to one storage device each so that the stored measured values will at least approximately perpendicularly to the direction of movement of the web correspond to adjacent web sections while the measured values will be derived from the storage devices for indicating or registering the transverse profile or for control purposes.

By employing a plurality of moisture gauges it will also be possible simultaneously to ascertain the respective moisture content for each section of an imaginary line which extends in a direction transverse to the direction of movement of the web.

According to a preferred method of the present invention, the electrically measured values of the moisture gauges are continuously and respectively conveyed to storage condensers with a discharge resistance while at the time when a transverse profile is being measured, the current supply of the moisture gauge as well as the discharge current circuit of each discharge resistor is interrupted so that the measured values obtained at the time of the measuring operation and pertaining to the moisture gauges remain stored in the storage condensers. The obtained measured values are conveyed to the storage means or devices so that they can remain stored practically for any desired length of time. For purposes of registering, the measured values are, for instance, withdrawn from the storage devices one after the other while each individual withdrawal of a measured value is extended over such a long time period that the inertia or lag of the registering instrument will not affect the measurement so that for each measured value a corresponding precise registration will be obtained. Preferably, the registration is effected on a registration tape which is advanced at the rhythm at which the individual stored measurements are withdrawn from the storage devices, said registration tape being advanced in conformity with the local sequence of the moisture gauges. In this way, a very il lustrative picture is furnished concerning the distribution of the moisture content of the web material. If desired, the individual measured values may, for instance, successively be conveyed to a printing device which prints the respective moisture content in the form of figures. For purposes of eliminating errors, for purposes of control or regulation and also as proof for possible complaints about the quality of a paper roll, such obtained measured results are an excellent evidence. In view of the measuring results obtained in this way, it has become possible for the first time to adapt or control the moisture content of a web being moved in conformity with the respective prevailing conditions. Advantageously, each breast box lip has associated therewith a moisture gauge so that the control of the pulp supply can be effected selectively. Instead of controlling the position of the breast box lips in order to obtain a uniform moisture content of the web over the entire width thereof, it is also possible to employ a drier which by means of hot air selectively dries the web.

According to a further development of the method according to the invention, it is possible simultaneously with or separately from the registration of the transverse profile of the moisture content, to withdraw the measured values at such a fast sequence and to convey the same to a registering instrument so that in view of the inertia of the registering instrument substantially the mean value of the moisture content of the web is registered whereas greater deviations from the mean value will remain recognizable. When values of the moisture content occur which considerably differ from the mean value, corresponding changes in the course of the medium line occur which will clearly point to possible sources of error. For instance, in view of inaccuracies at the drying areas of the paper machine, changes in the moisture conditions may occur periodically or at regular time intervals or distances. While such changes in the moisture condition may extend over the entire length of the web, they are rather limited in the longitudinal direction of the web. Such variations cannot or can only accidentally be caught or picked up by the measuring according to the invention of the moisture distribution. The feed of the registering tape of the registering instrument for the mean value is expediently effected proportionally with respect to the respective speed of the web. For purposes of forming the mean value of the moisture content, also the total of the currents flowing through the discharge resistors of the storage condensers may be employed.

The present invention relates not only to a new method but also covers a device for carrying out the new method. This device is characterized primarily in that a number of moisture gauges which corresponds to the number of the breast box lips of the paper machine is arranged transverse to the direction of movement of the web while the moisture gauges are located adjacent to each other and parallel to the plane of said lips and on a common support. Within the region of said lips there are provided openings for the suction air whereby the web is held in contact with the moisture gauges. In view of the fact that the moisture gauges are arranged adjacent to each other, it is possible with dimensions of, for instance, centimeters of a moisture gauge in the direction transverse to the direction of movement of the web to realize a satisfactory distinction between the various moisture contents of the web material in a direction transverse to the movement of the web. By employing suction air, the web will be held in continuous contact with the moisture gauges so that no errors can occur in view of a temporary fluttering or lifting off of the web from the moisture gauges.

A special embodiment of the device according to the present invention is characterized in that the moisture gauges are arranged in a housing which is open substantially only toward the web while the housing walls which face the web and which together with the moisture gauges form the openings are flush with the moisture gauges, said housing being connected to an exhauster.

Advantageously, the housing comprises substantially an I-beam having one side covered and forming an air passage for the suction air, whereas the moisture gauges are arranged on the other side. The costs of such a housing are relatively low while the best possible rigidity or strength is important for a precise measuring operation.

Referring now to the drawings in detail, FIG. 1 illustrates a support 1 resting on stands or legs 2. Connected to the support 1 are moisture gauges 3 the measuring indicators of which face the web 4 being moved. The extension of the moisture gauges in a direction transverse to the direction of movement of the web is preferably as small as possible in order to obtain a good subdivision of the measured transverse profile of the moisture content of the web.

For purposes of controlling the breast box lips of the paper machine, the measuring range of each moisture gauge should approximately equal the width of a lip.

FIG. 1 furthermore diagrammatically illustrates an answering device 5 which is operatively connected to the moisture gauges 3. Connected to the answering device 5 are registering instruments 6 and 7. The registering instrument 6 serves for recording the transverse profile of the moisture content of the web material, whereas the registering instrument 7 serves for recording the mean value of the moisture content.

Further details of the electric circuit of the moisture gauges and of the answering device as well as of the subsequent structural elements are shown in FIG. 2.

As will be seen from FIG. 2, which illustrates by way of example the electric circuit for the moisture gauge 3 operates in conformity with the dielectric principle. The measuring gauge 3 has as measuring value emitter a measuring condenser 8 the capacity of which is affected by the dielectric constant of the web material, for instance, of the paper. Arranged in parallel with the measuring condenser 8 is a coil 9 which together with the measuring condenser 8 forms an oscillatory or resonant circuit 8, 9. Through the intervention of a decoupling condenser 10, a high frequency generator 11 is connected to the resonant circuit 8, 9. The generator 11 is supplied with current through a terminal l3 and can be turned on by means of a switch 12. The voltage at the resonant circuit 8, 9, the magnitude of which depends on the respective moisture content of the web material, is through a diode 14 conveyed to a condenser 15. Furthermore, the condenser 15 is through a diode 16 and a resistor 17 connectable to a terminal 18 which receives a voltage directed opposite to the forward direction of the diode 16, said last mentioned voltage exceeding the voltage which after a measuring operation prevails at the condenser 15. This counter voltage at the terminal 18 is adapted to be made effective through a switch 19. For instance, the switches 12 and 19, as illustrated, are coupled mechanically so that simultaneously with the turning on of the counter voltage at the diode 16, the current supply for the high frequency generator 11 is interrupted. This brings about that the value for the moisture content of the respective range of the web which value was stored after a measuring operation, will for all practical purposes be available for a sufficiently long period of time. For carrying out a measuring operation, the switches 12 and 19 are moved into a position which is opposite to the direction shown in FIG. 2. As a result thereof, high frequency energy is conveyed to the resonant circuit 8, 9, and the condenser charges itself up to a voltage which corresponds to the respectively prevailing moisture content of the web.

The condenser 15 is connected to one of the contacts 20 of an answering device 21. The device 21 has, for instance, a contact arm 22 which is moved by a stepping motor 23. The stepping motor 23 is connected to a rhythm generator 24. By means of acontrol handle 25, the sequence frequency of the individual rhythm or control impulses for the stepping motor can be controlled. For purposes of withdrawing the measuring values of the condensers 15 of the moisture gauge 3, such rhythm frequency may be set that the contact arm 22 will for two seconds be located opposite a contact 20. This time will suffice with the prevailing inertia of a registering instrument, especially a writing registering gauge, to record the proper measured value.

In FIGS. 1 and 2 there are diagrammatically illustrated recording instruments for the transverse profile of the moisture content and there are also illustrated writing instruments for the mean value. Instead of such writing instruments, however, also printing devices may be provided which are adapted to print the respectively obtained measured values. The feed of the recording tape of the registering instrument 6 is synchronized with the answering device 21 so that the recorded transverse profile of the moisture content corresponds to the local sequence of the moisture gauge with regard to the web being moved. The feed of the registering tape for the mean value of the moisture content is proportional to the respective speed of the web 4. Thus, for each web or roll of paper or the like measured values are recorded which indicate the moisture content of the web in a so-called transverse profile and also for a mean value. The measuring of the transverse profile of the moisture content can be effected at regular time intervals, for instance, at intervals of five minutes.

The recording of the mean value of the moisture content may be effected by the same answering device 21 or by another answering device. In this connection it is merely necessary to turn on, for instance, the contacts 20 of the answering device 21 in sufficiently fast succession one after the other and to connect the same to the recording instrument, for instance, through a further amplifying means. For instance, the terminals 20 for all condensers 15 may in a uniformly distributed manner, be arranged on a circular line, and the stepping motor 23 could by means of the rhythm generator 24 be controlled in such a way that, for instance, in one second the contact arm 22 performs one revolution. This speed should be sufficiently high in most instances in order, in view of the inertia or lag of the recording instrument 17, to record substantially a mean value of the moisture content and during greater deviations from the mean value to indicate a deviation in the course of the recorded line. In this way conclusions concerning possible errors, especially periodically occurring errors are possible which during the measuring of the transverse profile of the moisture content could not or could only accidentally be recorded.

The formation of the mean value of the moisture content may also be effected in such a way that the total is formed of the currents flowing through the re sistors 17 and is conveyed to an indicating and/or registering instrument. Instead of the answering device 21, also an electronic slide recorder may be employed with the same success.

It will be understood that instead of the moisture gauges above referred to, also moisture gauges can be employed which follow different principles without affecting the essence of the present invention.

In FIG. 3, the support 1 for the moisture gauges 3 is shown in section. The support 1 is through a pipe 27 connected to an exhauster. The hollow support 1 which is composed of an I-beam forms with the measuring condensers & of the moisture gauge 3 openings 28 through which air is drawn. At one side the support 1 is covered by a plate 29 so that an air passage 30 is formed to which the said exhauster is connected. In view of the effect brought about by the suction air, the web 4 remains in constant contact with the measuring condensers 8 or other measuring value emitters of moisture gauges. Expediently, the structural elements of each moisture gauge 3 are mounted in control boxes 26 which are connected to the support 1.

It is, of course, to be understood that the present invention is, by no means, limited to the particular showing in the drawings but also comprises any modifications within the scope of the appended claims.

What I claim is:

1, An apparatus for measuring the transverse profile of the moisture content of web material, especially paper, moving along a path, which includes: supporting means, a plurality of individual moisture gauges for measuring moisture content in the web and supported by said supporting means one behind the other and adapted to be placed parallel to and across the web to be measured, electric storing means including a storage condenser respectively electrically connected to each of said moisture gauges for storing the respective moisture content ascertained by said moisture gauges when extending across a moving web, the moisture contents of which is to be measured, indicating means, and means for conveying the stored ascertained moisture content from said electric storing means to said indicating means for visually indicating-the said ascertained moisture content, a discharge resistor connected electrically parallel to each of said storage condensers only during predetermined times, and switch means operable to interrupt current supply to said moisture gauges and to each discharge resistor so that the measured moisture content ascertained by the moisture gauges during a measuring operation will remain stored accordingly in said storing condensers for a desired period of time.

2. An apparatus according to claim 1, which includes means for successively withdrawing the measured moisture content in conformity with the local succession of said moisture gauges, and means for conveying each measured moisture content to said indicating means over a minimum time period in conformity with the said indicating means, said indicating means including tape means advanced in synchronism with the withdrawal of the respective moisture values from said storing means.

3. An apparatus according to claim 2, which includes control means operatively connected to said moisture gauges and operable to act upon that respective portion of the web material to be moisture measured which corresponds to the respective moisture gauge. 

2. An apparatus according to claim 1, which includes means for successively withdrawing the measured moisture content in conformity with the local succession of said moisture gauges, and means for conveying each measured moisture content to said indicating means over a minimum time period in conformity with the said indicating means, said indicating means including tape means advanced in synchronism with the withdrawal of the respective moisture values from said storing means. 